The desirability of purifying and deodorizing interior air for vehicles and airplanes is well known to users and people who work in such an environment. Those skilled in the art are familiar with devices which have been offered to address this need. Electrostatic filtering devices or precipitators ionize, or electrically charge, particulate in the incoming air stream to facilitate its removal. Ionization is achieved by exposure to an electrical field of as much as 6,000 volts, which is confined to a small area to produce an extremely intense field. A thin wire, stretched across the air flow path, displays this small area to best effect and a series of these wires are usually spaced to cover the entire path. The ionized air flow is then directed to pass through an alternating array of like and oppositely charged plates where the charged particulate is repelled by the like charge and attracted to the opposite charge for collection.
In a stationary system, size and weight are not critical and shock loading is not a consideration but in a mobile these factors become paramount. Ideally, such a unit should remove smoke and particulate down to sub-micronic matter, bacteria and viruses, but size and weight limiting considerations have caused typical current mobile electrostatic filtering devices to perform in the 5 micron range. An ionizing wire and collecting plate array form a complex structure with each plate insulated from its neighbors and moreover, a structure which must be open to permit free air flow, rigid to maintain critical spacing and shock mounted to prevent damage. As a result, filter makers will dispense with the ionizing wire while sacrificing efficiency in order to make a more rugged unit for vehicular service. Furthermore, to avoid frequent need for time consuming plate cleaning procedures and possible damage by users, manufacturers currently recommend that their automotive units be used only for limited periods. In this manner, plate cleaning can be treated as an item of scheduled vehicle maintenance and done only by trained personnel.
Thus, an object of the present invention is to provide a self-contained, light weight, compact electrostatic filtering unit which is suitable for installation in any vehicle or airplane. A second object is to provide such a unit without any compromise of its performance. A third object is to equip this unit with an ionizing wire and collecting plate array which is sufficiently simple and rugged that the user can readily remove it, wash it in a home dish washer and reinstall it.
These objects are realized in the present invention by a novel configuration of an ionizing wire/collecting plate array wherein the wires are mounted directly to extended portions of like charged plates so as to extend along the width thereof and are positioned in an alternating series between oppositely charged plates. This permits a compact assembly of the ionizing wire and collecting plates which can be easily removed and replaced as a unit. Preferred embodiments of the invention also include means for directing the air flow to contact collecting plate surfaces while passing therebetween, thereby enhancing collection efficiency and various auxiliary pre-filtering or post-filtering means.